When a frame, as one transfer unit, comprising a transmitting party address, a destination party address, data, etc, is transmitted through a LAN of a CSMA/CD type having a plurality of stations such as servers and clients connected thereto, transmission of the frame is executed when an idle state is detected by detecting the existence/absence of a carrier on a LAN (a carrier sensee), that is, by detecting whether a LAN is busy (a frame exists) or idle (a frame is absent). The station that transmits the frame monitors collision with frames transmitted from other stations (collision detection). Upon detecting collision, the station transmits a jamming signal for a predetermined time, positively notifies collision to other stations and then suspends transmission. After waiting for an arbitrary time, the station repeats the state monitor and attempts to again transmit the frame.
When HTTP is used for communication between a server and a client, the communication needs time depending on the processing capacity of the server, the busy time of the LAN becomes longer, and the possibility that the client must wait becomes greater.
As a system for executing control so as to decrease traffic on a LAN, a system that disposes a proxy server between the server and the client is known. In a proxy server system, when the client sends a transmission request, for an object, to the server, the proxy server receives the transmission request, returns it to the server, receives an object corresponding to the transmission request from the server, and transmits the object so received to the client. The proxy server stores the transmission request and the object received in response to the transmission request in a storage unit. When the client thereafter generates the same transmission request, the proxy server directly transmits the object corresponding to the transmission request and stored in the storage unit to the client without passing through the server. In this way, it becomes possible to reduce the delay time in communication, resulting from the processing capacity of the server, or, to save the time necessary for transmitting the object corresponding to the transmission request after the server receives the transmission request.
In the proxy server system described above, however, the LAN remains always busy while each client generates the transmission request to the server even though the transmission request stored in the storage unit of the proxy server coincides with the one generated by the client. In other words, this system cannot sufficiently reduce the traffic on a LAN.